Primers and conductive primers are well known in the art and are widely used in the manufacture of automobiles and trucks. High solids conductive primers used over plastic parts are also well known, as shown in Tremper U.S. Pat. No. 4,740,426 issued Apr. 26, 1988; Tremper U.S. Pat. No. 4, 740,566 issued on Apr. 26, 1988; and Tremper U.S. Pat. No. 5,068,063 issued on Nov. 26, 1991. However, none of these compositions have the ability to dry and form conductive materials at ambient temperatures or low bake temperatures.
In modern auto and truck manufacturing facilities, a topcoat paint is applied by electrostatic spraying. Electrostatic spraying reduces paint loss and air pollution caused by paint over-spraying. To efficiently electrostatically spray a paint, the substrate must be conductive. Most autos and trucks contain flexible plastic components and some auto bodies are constructed entirely from a polymer reinforced fiber glass and others from plastic. These components are not electrically conductive and electrostatic spraying works poorly over such substrates. Also, these components are flexible and require primer and topcoat that is flexible. Another major challenge that faces automotive and truck manufacturers is how to rapidly cure the primer, to render the substrate conductive, using minimal investment in floor space, flash times, and flash drying and baking zones. Conventional primers are unable to cure to a sufficiently conductive state in a relatively short period of time at low temperatures, and thus the productivity and energy efficiency of the painting operation is currently lacking.
There is a great need in auto and truck manufacturing for a high quality primer that is electrically conductive, flexible, has excellent adhesion to the substrate, provides a surface to which conventional coatings will adhere, and that will rapidly cure to a conductive state at ambient or slightly elevated temperatures which would reduce energy cost and increase productivity.
The novel primer composition of this invention has the aforementioned desirable characteristics.